1. Field of the Invention
The present invention relates to a vertebral spacer for artificial vertebrae and more particularly, to an adjustable vertebral spacer that allows adjustment of the height (length) and tilting angle.
2. Description of the Related Art
In a vertebral body replacement, a vertebral spacer for artificial vertebrae is usually used to replace or treat the anterior column of the spine after the resection of spinal tumors or severely fractured anterior spinal elements. By means of a surgery operation the diseased vertebral body is resected, and a vertebral spacer is installed to replace the resected vertebral body, and affixed in place by means of a pedical screw or vertebral plate, resuming the function of the patient's spinal column.
Conventional vertebral spacer designs include two types, i.e., the mesh cage type and the adjustable type. FIG. 1a shows a cage type vertebral spacer 10. The mesh cage type vertebral spacer 10 is properly cut subject to the length of the resected vertebral body so that the vertebral spacer 10 can be set in between the adjacent upper and lower vertebral bodies. The major drawback of this design of mesh cage type vertebral spacer 10 is the non-adjustability of the height, and it needs to be trimmed several times during the surgery operation, wasting much the operation time. Further, the lordosis angle between the horizontal angle-like irregular spikes and the vertebral endplate does not match, and the spikes pierce the vertebral endplate, accelerating sagging.
FIG. 1b shows an adjustable design of vertebral spacer 20. According to this design, the top and bottom endplates 20a are respectively fastened to the spacer body of the vertebral spacer 20 by means of a screw joint so that the endplates 20a are rotatable to adjust the height of the vertebral spacer 20. However, the fusion and fixation stability between the endplates 20a and the spinal column of the patient determines the successbility of the vertebral body displacement. The reasons of failures in surgical operations using this adjustable design of vertebral spacer 20 include (1) slipping of the adjustable vertebral spacer from the predetermined position, and (2) sagging of the artificial vertebral spacer or piercing the artificial vertebral spacer through the adjacent upper and lower vertebral bodies to cause vertebral destruction.
Therefore, it is desirable to provide a vertebral spacer that eliminates the aforesaid problems.